I went from Los Angeles to the Dublin shows in 1993. A friend in Dublin arranged for me to have a ticket for the first night, but for the second night I was on my own to get a ticket. Without ever searching hard, I purchased a ticket outside that night for 5 Irish pounds over the face on the ticket which in reality probably was about face value, when you add in service charges paid by the original buyer. The RDS capacity for these 2 shows was roughly 38,000 each night, so less than 1/2 of the total played to at the 2 Slane shows.
A friend of mine went to the second Slane show in 2001 and told me that outside the venue, people couldn't get rid of tickets. They probably were not scalpers, but people who had friends drop out form going on the actual day. He said he saw people give up and walk in with their extra tickets, due to a lack of people without tickets showing up in hopes of buying.
A big difference this year though is that the shows are in the heart of Dublin, thus you should expect more walk up crowds looking for tickets than in 2001, since Slane is a small town outside of Dublin, so it took more effort for people to get there to investigate if there were any tickets to be had.
